1. Field of Invention
The invention relates to a control apparatus for an automatic transmission installed in a vehicle and, more particularly, to a control apparatus for an automatic transmission capable of performing neutral control.
2. Description of Related Art
In some known automatic transmissions for a vehicle, if the vehicle stops in a forward drive range, the control for releasing an input clutch (hereinafter referred to as "neutral control") is performed for the purpose of improving fuel consumption.
According to the related art, the clutch is released after the lapse of a predetermined length of time from a time when a vehicle speed detected by a vehicle speed sensor becomes zero, by estimating a time when the vehicle is definitely stopped.
However, during the aforementioned control, while the pressure of hydraulic fluid in a hydraulic servo of the input clutch needs to be reduced drastically from a normal line pressure to a release pressure, the hydraulic pressure needs to be released gently to prevent a shock from being caused when releasing the clutch. Therefore, it takes a long time until the operation is completed, and a time lag is generated from the stop of the vehicle to the actual release of the input clutch. As a result, the effect of the neutral control is lessened.